(1) Field of the Invention
This invention relates to a method for grafting a porous element for leucodepletion, as well as the porous element obtained by this method, a filtration unit comprising such a porous element and a pouch system comprising such a filtration unit.
The invention typically applies to the filtration of blood or a blood component such as whole blood or packed red blood cells, as well as to the separation and collection of blood components, particularly in a closed circuit.
(2) Prior Art
Leukocytes have very significant undesirable effects, which has resulted in a search to eliminate them from the blood components intended for transfusion. As a matter of fact, leukocytes increase the risks of immune rejection, such as graft versus host disease, and promote the transmission of infectious agents.
In order to eliminate leukocytes from the blood components intended for transfusion, filtration units are already known, which comprise a casing containing a leucodepletion medium. In such units, the leucodepletion medium includes one or more membrane(s) and/or one or more layer(s) of a non-woven fabric made of a polymer material and treated so as to improve the leucodepletion rate, the recovery of the blood components, and the filtration priming time and/or filtration selectivity, e.g., by allowing the platelets to pass through.
For example, document EP-A1-0 606 646 describes a filtration unit the leucodepletion medium of which is coated with a polymer comprising basic functional groups and non-ionic hydrophilic groups, such as poly(ethylene glycol) groups, the proportion between the basic groups and the hydrophilic groups being chosen so as to obtain a low rate of residual leukocytes and high-efficiency recovery of the red blood cells.
In this document, the coating is made in two steps. These steps consist in the radical copolymerization of a basic monomer and a hydrophilic monomer, and then simple impregnation of the filtration medium with a solution of the resulting copolymer. This means that the polymer coating is not covalently bonded to the leucodepletion medium, thereby causing a risk of elution of the copolymer into the filtrate. Furthermore, radical polymerization requires the use of a polymerization initiator, which may also end up in the filtrate, and which is not recommended.
In the same way, document US-20060207937 describes a filtration unit intended to eliminate the leukocytes from whole blood, which comprises a leucodepletion medium coated with a polymer obtained by reaction of a hydrophobic monomer and a hydrophilic monomer. Again, the polymer coating is not covalently bonded to the surface of the leucodepletion medium.
Finally, in document WO2007/054638, the leucodepletion medium of the filtration unit intended to eliminate the leukocytes by allowing the platelets to pass through is impregnated with a block copolymer consisting of a hydrophilic block of the poly(ethylene oxide) type and two hydrophobic blocks.
In all of these documents, it appears that the coating of a leucodepletion filter consists of a block copolymer comprising hydrophilic and non-hydrophilic portions.